Dear Editor, The biological importance of glutamine lies in its being a major source of carbon and nitrogen for both catabolic and anabolic demands. Glutamine is converted to glutamate and then to a-ketoglutarate (a-KG), a catabolic process known as glutaminolysis. a-KG enters the tricarboxylic acid (TCA) cycle, referred to as anaplerosis, not only for the generation of ATP via oxidative phosphorylation, but also for the production of acetyl-coA as a critical precursor for the synthesis of lipids and nucleotides. This is particularly true in cancer cells where glutamine is even considered as a conditionally essential amino acid because its cellular demand often exceeds the rate of self-supply, owing to glucose being ineffectively utilized for energy production through aerobic glycolysis and diversion to biosynthesis.1,2 Glutamine also plays a vital role in clearing reactive oxygen species (ROS), not only by providing the precursors glutamate and cysteine for the synthesis of GSH, but also by promoting the production of NADPH via glutamate dehydrogenase (GLUD) or the aspartate/malate shuttle.3 In cancer cells, deprivation of glutamine results in a large increase of ROS, damaging the structure and function of mitochondria.4 When the
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